Self-cleaving RNAs, termed ribozymes, are unique in nature since these macromolecules catalyze their own processing reactions with extreme precision. Any error in the cleavage step for this genetic material could result in a lethal genetic mutations for the donor system. Since ribozymes have been shown to be active with a variety of primary sequence modifications in the active site, secondary and ternary structural interactions must play a key role. We are using time-resolved fluorescence lifetime and polarized fluorescence methods on probe labeled HDV RNA to investigate: (1) structural transitions between the inactive conformation of HDV RNA in the presence and absence of metal cation; (2) the location of loop versus stem regions in the RNA structure to compare with competing published RNA structures; (3) dynamic changes in the loop and stem structure with external perturbations; (4) the role of the 3' terminus in stabilizing the active structure in the active site domain; (5) two and three point energy transfer studies to measure distances which will provide constraint parameters for the theoretical energy minimization calculations.